WO 03/054771 A1 discloses an electric toothbrush comprising a handpiece and a replaceable brush attachment. The brush attachment accommodates a memory in which information identifying the brush attachment is stored. Furthermore, the brush attachment houses a transponder that delivers the information stored in the memory upon receiving an interrogation signal from an interrogation station. The handpiece houses a microcontroller capable of computing the cumulative usage of the identified brush attachment and writing it into the memory of the brush attachment. The handpiece is also equipped with an indicator for indicating the need for replacement of a brush attachment.
DE 102 47 698 A1 discloses an electric toothbrush comprising a handpiece and a replaceable bristle head. The handpiece is provided with a display on which an end of use indication for the bristle head can be shown.